Amino acid concentrations and selected enzyme activities in rat auditory, olfactory, and visual systems.

Homogenates of specific brain regions of three sensory systems (auditory, olfactory, and visual) were prepared from pigmented Long-Evans Hooded rats and assayed for amino acid concentrations and activities of glutaminase, aspartate aminotransferase (total, cytosolic, and by difference, mitochondrial), malate dehydrogenase, lactate dehydrogenase, and choline acetyltransferase. Comparing the quantitative distributions among regions revealed significant correlations between AAT and aspartate, between glutaminase and glutamate, between glutamate and glutamine, and between AAT plus glutaminase, or glutaminase alone, and the sum of aspartate, glutamate, and GABA, suggesting a metabolic pathway involving the synthesis of a glutamate pool as precursor to aspartate and GABA. Of the inhibitory transmitter amino acids, GABA concentrations routinely exceeded those of glycine, but glycine concentrations were relatively high in brainstem auditory structures.

Immunohistochemistry of muscarinic acetylcholine receptors in rat cochlear nucleus.

Neurons of the cochlear nucleus (CN) receive extrinsic and intrinsic cholinergic inputs, the effects of which appear to be mediated primarily by muscarinic acetylcholine receptors (mAChRs). To investigate the distribution of mAChRs and the correlation of pre- and post-synaptic cholinergic markers in CN, we used a monoclonal anti-mAChR antibody (M35) and a monoclonal antibody against choline acetyltransferase (ChAT) to perform immunohistochemistry on rat brain sections, and we also carried out histochemistry for acetylcholinesterase (AChE) activity. The density distributions of ChAT immunohistochemistry and AChE activity histochemistry agreed well with previous quantitative measurements of the activity distributions of these enzymes.

Muscarinic receptor subtypes in rat dorsal cochlear nucleus.

We previously reported that responses of spontaneously active rat dorsal cochlear nucleus (DCN) neurons to cholinergic agonists are mediated predominantly by muscarinic receptors. We have now tested the effects of 7 antagonists with differing affinities for the muscarinic receptor subtypes M1-M4 on the responses to constant, submaximal doses of carbachol in rat brainstem slices. Each slice was exposed to one or more concentrations of one antagonist applied during extracellular recording of a DCN neuron.

Isolation of Trypanosoma brucei gambiense from northern Uganda: evaluation of the kit for in vitro isolation (KIVI) in an epidemic focus.

867 individuals from 3 sites near the town of Adjumani in the East Moyo region of north-west Uganda were investigated clinically and serologically for evidence of current trypanosome infections. Blood samples were taken from 94 persons with a positive card agglutination test for trypanosomiasis (CATT) and clinical suspects and inoculated into the kit for in vitro isolation of Trypanosoma brucei gambiense (KIVI). Amongst this group, 30 parasitaemic individuals were identified by microhaematocrit centrifugation and the quantitative buffy coat technique (QBC).

Thymic emigration: conveyor belts or lucky dips?

The thymic medulla has always seemed a rather uncomplicated compartment, simply storing mature thymocytes until they are exported to the peripheral lymphoid organs. However, as discussed here by Roland Scollay and Dale Godfrey, a careful look at recent data suggests that events in the medulla may be more complex and protracted than previously thought.

Comparison of surgeries for removal of primary vestibular inputs: a combined anatomical and behavioral study in rats.

Unilateral removal of Scarpa's ganglion and neurectomy of the peripheral vestibular nerve branches were compared in rats as methods to eliminate primary vestibular input. Ocular nystagmus was consistently observed after both types of lesion, but it completely disappeared within 4 to 7 days. Imbalance and rotation were more serious and prolonged after ganglionectomy than after peripheral neurectomy.

CD38 expression on mouse T cells: CD38 defines functionally distinct subsets of alpha beta TCR+CD4-CD8- thymocytes.

We have examined CD38 expression on mouse lymphocytes using the rat mAb NIM-R5 and demonstrate that CD38 expression is restricted to approximately 8% of thymocytes. Although CD38 is absent from the majority of CD4+CD8- and CD4-CD8+ T cells, we detected a strong correlation between CD38 expression and alpha beta+CD4-CD8- T cells in the thymus, with nearly 80% of alpha beta TCR+CD4-CD8- thymocytes being CD38+. Using heat stable antigen (HSA) and CD38, we divided alpha beta+CD4-CD8- thymocytes into four subsets: HSA+CD38-, HSA-CD38hi, HSA-CD38low and HSA-CD38-.

Quantitative distribution of amino acids in the rat vestibular nuclei.

The normal concentrations of 12 amino acids in the vestibular nuclei of rats were quantitatively measured using microdissection of freeze-dried brain sections combined with high performance liquid chromatography (HPLC) analysis. Both excitatory amino acids, aspartate and glutamate, showed only small variation across the vestibular nuclei. The distribution of glutamine tended to parallel that of glutamate.

A comparison of parasitological methods for the diagnosis of gambian trypanosomiasis in an area of low endemicity in Côte d'Ivoire.

The card agglutination test for trypanosomiasis (CATT) was used to examine 8974 inhabitants in 14 village areas south-west of Daloa, Côte d'Ivoire; 114 (1.3%) were CATTT or +/-, and were further examined by one or more of 6 methods for the direct detection of trypanosomes: lymphatic gland puncture, stained thick blood film (TBF), haematocrit centrifugation technique (HCT), mini-anion exchange column (MAEC), quantitative buffy coat method (QBC), and kit for in vitro isolation of trypanosomes (KIVI). Trypanosomes were seen by at least one method in 16 (14.

Cholinergic modulation of spontaneous activity in rat dorsal cochlear nucleus.

Extracellular recordings were made from brain stem slices to test the effects of bath application of cholinergic agonists and antagonists on the firing rates of spontaneously active dorsal cochlear nucleus neurons. About 90% of neurons responded to carbachol. A higher proportion responded to muscarine than to nicotine.

Aspartate aminotransferase and glutaminase activities in rat olfactory bulb and cochlear nucleus; comparisons with retina and with concentrations of substrate and product amino acids.

The quantitative distributions of aspartate aminotransferase and glutaminase were mapped in subregions of olfactory bulb and cochlear nucleus of rat, and were compared with similar data for retina and with the distributions of their substrate and product amino acids aspartate, glutamate, and glutamine. The distributions of both enzymes paralleled that of aspartate in the olfactory bulb and that of glutamate in the cochlear nucleus. In retina (excluding inner segments), there were similarities between aspartate aminotransferase and both glutamate and aspartate distributions.

Onset of TCR-beta gene rearrangement and role of TCR-beta expression during CD3-CD4-CD8- thymocyte differentiation.

TCR-beta gene rearrangement or expression is necessary and sufficient for the progression of early alpha beta thymocyte differentiation from the CD3-CD4-CD8- triple negative (TN)3 to the CD4+CD8+ double positive stage. The onset of TCR-beta rearrangement is currently thought to occur gradually. Some thymocytes were reported to be rearranged at the earliest (CD44+CD25-) TN stage, whereas other thymocytes did not initiate TCR-beta rearrangement until the latest (CD44-CD25-) TN stage.

The persistence of genetic homogeneity among Trypanosoma brucei rhodesiense isolates from patients in north-west Tanzania.

Trypanosomes isolated during 1991 from nine patients with Rhodesian sleeping sickness in north-west Tanzania were genetically characterized by electrophoresis of ten enzymes. Eight isolates were allocated to a known zymodeme (Z306); another had an enzyme profile (Z379) not previously encountered. An example of Z306 has been previously isolated in 1971, nearby in a part of Rwanda adjacent to the border with Tanzania; in addition, a closely related isolate, in Z307, was collected in 1959 from a patient in north-west Tanzania.

IL-12 influences intrathymic T cell development.

IL-12 has been implicated in the maturation and activation of peripheral T lymphocytes and NK cells. In the present study we have investigated the potential role of IL-12 in intrathymic T cell development. Treatment of mouse fetal thymic organ culture with IL-12 caused a significant reduction in size and cell number compared with the untreated controls.

Monoclonal antibody 2D10 recognizes a novel T cell costimulatory molecule on activated murine B lymphocytes.

We have developed a panel of rat mAbs against dibutyryl cAMP-activated 5C2 cells. In this panel, one mAb, 1G10, recognized murine B7. Another mAb designated 2D10 did not bind to murine B7 but could recognize a surface molecule expressed only on dibutyryl cAMP-activated 5C2 mouse B lymphoma cells or on LPS-stimulated splenic B cells.

Thymic epithelial cell lines that mediate positive selection can also induce thymocyte clonal deletion.

Negative selection of potentially autoreactive thymocytes occurs mainly in the thymus and is thought to be induced primarily by interaction with bone marrow-derived cells. However, some studies have also reported a role for radioresistant thymic cells, which are probably epithelial in origin, in the deletion of thymocytes reacting to endogenous superantigens. We have previously demonstrated that thymic epithelial cell lines could induce thymocyte-positive selection in vivo.

Functional characteristics of spontaneously active neurons in rat dorsal cochlear nucleus in vitro.

1. The cochlear nucleus of rat brain stem slices was explored with extracellular microelectrodes to determine the distribution and characteristics of spontaneously active neurons. 2.

Expression and functional analysis of murine B7 delineated by a novel monoclonal antibody.

The B cell surface molecule designated B7 has been shown to be expressed by activated human B cells and monocytes and to be a ligand for the CD28 and CTLA-4 molecules on T cells. B7/CD28 interactions can provide a second signal to T cells (in addition to occupancy of the T cell antigen receptor) that is needed for T cell activation. COS cells transfected with the mouse homologue of B7 have been demonstrated to provide a stimulatory signal to murine and human T cells.

Flow cytometric analysis reveals unexpected shared antigens between histologically defined populations of thymic stromal cells.

Utilizing flow cytometry, the expression of antigens recognized by six thymic stromal cell (TSC) reactive mAbs was investigated on fresh TSCs and TSC lines. It was found that some thymic epithelial cells and dendritic cells share antigenic phenotypes, and that most TSC reactive mAbs have a more extensive distribution than would have been predicted from immunohistology. While these findings illustrate the higher sensitivity of flow cytometric analysis, they more importantly emphasize the great complexity of TSC that direct T cell development.

Isolation of a cDNA encoding thymic shared antigen-1. A new member of the Ly6 family with a possible role in T cell development.

We have previously characterized a novel mouse thymocyte marker, defined as thymic shared Ag-1 (TSA-1), present on both immature thymocytes and a subset of thymic medullary epithelial cells. MTS 35, a mAb specific for TSA-1, alters T cell differentiation when added to fetal thymic organ cultures, suggesting TSA-1 may be important for T cell development in the thymus. In this study, we describe the isolation of a cDNA encoding TSA-1 using transient expression of COS-7 cells and selection with MTS 35.

A lymphostromal molecule, thymic shared Ag-1, regulates early thymocyte development in fetal thymus organ culture.

Previously, we detailed the characterization of thymic shared Ag-1, a unique marker of immature thymocytes and isolated thymic stromal cells, defined by the mAb MTS 35. In this study, the functional relevance of this molecule to thymopoiesis was investigated by the addition of purified MTS 35 to fetal thymus organ culture. It down-regulated thymic shared Ag-1 expression and dramatically reduced thymocyte cell yield through inhibition of alpha beta-TcR+ T cell differentiation, post CD3-CD4-CD8- triple negative thymocytes.

Control points in early T-cell development.

Intrathymic T-cell differentiation involves the generation, expansion and selection of distinct T-lymphocyte subsets. While positive and negative selection have been a focal point of T-cell development, these events represent the final stages in a complicated sequence of differentiation steps. Here, Dale Godfrey and Albert Zlotnik summarize recent advances in our understanding of early T-cell development and describe five 'control points' that identify key events in this sequence.

ER-MP12 antigen, a new cell surface marker on mouse bone marrow cells with thymus-repopulating ability: II. Thymus-homing ability and phenotypic characterization of ER-MP12-positive bone marrow cells.

In the accompanying paper we showed that six distinct subsets of bone marrow (BM) cells can be identified using the mAb ER-MP12 and ER-MP20 in two-colour immunofluorescence analysis. Upon intrathymic transfer into sublethally irradiated mice thymus-repopulating ability was restricted to ER-MP20- BM cells expressing either high or intermediate levels of the ER-MP12 antigen (1-2% and approximately 30% of BM nucleated cells respectively). The highest frequency of thymus-repopulating cells was found in the minor subset of ER-MP12(+)+20- BM cells.

Choline acetyltransferase in cochlear root neurons.

Cochlear root neurons are a distinct group of cells located in the auditory nerve root in small rodents. Their transmitter is still unknown. Some of our preparations showed immunoreactivity of somata of cochlear root neurons with both polyclonal and monoclonal antibodies against choline acetyltransferase (ChAT) which, despite their very weak histochemical reaction for acetylcholinesterase (AChE), suggested that cochlear root neurons might be cholinergic.